Process of producing low-carbon metals or alloys.



PATENTED MAY 23, 1905.

E. F. PRICE.

PROCESS OF PRODUCING LOW CARBON METALS 0R ALLOYS.

APPLICATION FILED DEC. 10, 1904.

UNITED STATES Patented May 23, 1905.

EDGAR F. PRICE, OF NIAGARA FALLS, NEIV YORK.

PROCESS OF PRODUCING LOW-CARBON METALS OR ALLOYS.

SPECIFICATION forming part of Letters Patent No. 790,397, dated May 23, 1905.

Application filed December 10, 1904. Serial No. 236,321.

'l'o all w/rom it may concern.-

Be it known that I, EDGAR F. PRICE, a citi- Zen of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have invented certain new and useful Improvements in Processes of Producing Low-Carbon Metals or Alloys, of which-the following is a specification.

In the production of ferrochromium from chromite it is customary to introduce a small charge of the ore, carbon, and a flux into an electric furnace having sides and a hearth of carbon and to spring an are between the hearth and a depending carbon electrode having its lower end embedded in the charge. A high potential difference is usually maintained between the terminals of the furnace. As the ore is reduced a layer of the ferrochromium accumulates on the hearth, covered by a layer of slag. The molten alloy is tapped out from time to time until the slag has increased to such an amount as to require removal. As the normal slag has a high fusionpoint, a flux is added to render it more liquid, and the remaining alloy and slag are linally run out through the metal tap-hole. The furnace is then charged anew, and the process is repeated.

It is important that the ferrochromium produced should be low in carbon. The amount of carbon in the charge is therefore ordinarily kept at a minimum. On account of the low percentage of admixed carbon, however, highly-oxidizing gases are evolved in contact with the depending electrode, which is soon consumed and must be replaced. The air also acts rapidly on the hot electrode when the furnace is emptied by the removal of slag. Since the charge is a fairly good conductor of electricity, a thin layer only is maintained around the lower end of the depending electrode to prevent excessive shunting of current to the carbon sides of the furnace under the high applied potential. Much heat is therefore lost by radiation from the zone of reduction through the charge, while the electrode is insufficiently protected from oxidation by the air. This loss of heat greatly decreases the reduction efficiency of the furnace. Furthermore, the slag 1s not kept at a sufliciently high temperature to permit it to be tapped out except by adding large amounts of flux, discontinuing the charging of ore, and employing the energy of the are merely to liquefy the slag. The heat losses are also increased by the discontinuous mode of working, both the furnace and the depending electrode cooling down when the furnace is emptied. It is also impracticable to efl'ecta clean separation of the metal and slag by removing them successively through a single tap-hole.

According to the presentinvention, the production of low-carbon ferrochromium and other metals and alloys is effected by a continuous operation comprising two stages. In the first stage an alloy with a relatively high percentage of carbon is produced by smelting a charge containing sufiicient carbon to protect the carbon electrodes. The molten highcarbon alloy is then tapped from the reduction-furnace and percolated through a granular body of a decarburizing agent-for example, lime-and the carburized reagent is separated from thelow-carbon product. The granular body is preferably heated by interposing it as a resistance-conductor in an electric circuit, both the heated lime and the percolating metal serving to carry the electric ,current.

Suitable apparatus for carrying out the process is shown in the accompanying drawing, in which the figure is a transverse vertical section of an electric reduction-furnace and a decarburizing-chamber.

The reduction-furnace comprises sides 1, of refractory non-conductive material, such as chromite or magnesia, and a hearth 2, of carbon, surrounded by a metal casing 8, having an electric terminal 3. The carbon hearth constitutes one electrode. The other electrode is a depending carbon rod 4. Tap-holes 5 6 extend through the side walls at different heights. In using this furnace to carry out the first stage of the process an arc is established between the depending electrode and the carbon hearth and a small amount of the charge for example, a mixture of chromite, coke, lime, and silica-is fed into the furnace. The charge preferably contains a considerable excess of carbon to protect the electrode A from oxidation. The furnace is then gradually filled until in its normal working condition the depending electrode is embedded in the charge. As the ore is reduced superposed layers of slag and ferrochromium collect in the bottom of the furnace and run out through the upwardly-inclined open tap-holes 5 6, the

alloy being delivered into the decarburizingchamber 7 More of the charge mixture is then fed into the reduction-furnace.

The decarburizing-chamber comprises a vertical annular body 8, of refractory non-con ductive material, preferably chromite or magnesia, surrounded bya metal casing 9. Beneath the body is a metal hearth 10, preferably a water-cooled steel casting, which serves as one electrode. A water-cooled metal ring 11,-arranged in the walls of the chamber near its upper end, serves as the other electrode. The chamber is filled with a granular body 12 of the decarburizing agentfor example, broken limewhich is supported by the metal hearth 10 and lies in contact with the inner surface-ofthe metal ring 11. Aheat-retaining hood 13 incloses the upper end of the decarburizing-compartment and the metal-outlet of the reduction-furnace. A tap-hole 14 extends from the lower end of the decarburizing-chamber.

In the second stage of the process the body of broken lime 12 in-the chamber? is initially raised to a high temperature, as by passing hot products of combustion through it, and the metal or alloy flowing from the tap-hole 6 of the reduction-furnace is delivered upon the upper end of the granular body and percolates slowly through it. The carbon of the alloy is thereby gradually withdrawn, reacting on the lime to produce calcium carbid. The carbid and decarburized alloy are delivered from the lower end of the chamber through the tap-hole 14 and are separated for example, by allowing them to stratifyin a receiving vessel and withdrawing the carbid and metal through tap-holes arranged at dif ferent heights. Any carbid which adheres to or is entangled with the metal is decomposed by treating it with water.

In order to maintain the granular body of lime at a high temperature, an electric current is passed between the metal hearth 10 and I the metal ringll and through the granular body and the molten metal therein, serving as a resistance-conductor. Both the heated lime and the percolating metal serve to carry the current.

I claim 1. The process of producing low-carbon metals or alloys, which consists in first producing a material relatively high in carbon, percolating the molten high-carbon product through a granular body of a decarburizing agent, and separating the carburized reagent from the low-carbon product, as set forth.

2. The process of producing low-carbon metals or alloys, which consists in first-producing a material relatively high incarbon, heating agranular body of a decarburizing agent by interposing the body as a resistanceconductor in an electric circuit, percolating the molten high carbon product through the heated granular body, and separating the carheating a granular body of a decarburizing agent by interposing'the body as a resistanceconductor-in anelectric circuit, percolating the molten high-carbon product through the heated granular body, and separating the carburized reagent from the low-carbon product, as set forth.

4:. The process of producing low -carbon metals or alloys, which consists in first producing a material relatively high in. carbon, percolating the molten high-carbon product through a granular body of highly-heated lime, and separating the resulting-calciumcarbid fromzthe lowwarbon-product, assetforth.

5. The process of producing low-carbon metals oralloys, which consists in first producing a material relatively high in carbon, heating a granular body oflimeto a high temperature-by interposing the body as a resistance-conductor in an electric circuit, percolating the molten high-carbon product through the heated granular body, and separating the resulting calcium carbid fromthe low-carbon product, as set forth.

6. The process of producing low-carbon metals or alloysywhich consists infirstproducing a material relatively high in carbon by electrically smelting acharge containing an excess of carbon, separating the resulting slag, heating a granular body oflime to a high temperature by interposing the body as a resistance-conductor in an electric circuit, percolating the-molten high-carbon product through the heated granular'body, and separatingthe resulting calcium carbid from the low-carbon product, as set forth. I

7. The-process of producing low-carbon ferrochromium, which consists in first producing ferrochromium relatively high in carbon, percolating the molten highcarbon product through a granular body of a decarburizing agent, and separating the carburized reagent from the low-carbon product, as set forth.

8. The process of producing low-carbonferrochromium, which consists in first producing ferrochromium relatively high in carbon, heating a granular bod-y ofa decarburizing agent by interposing the body as a resistance-conductor in an electric circuit,-percolating the molten high carbon product through the heated granular body, and separating the carburized reagent from the low-carbon product, as set forth.

9. The process of producing low-carbon ferrochromium, which consists in first producing ferrochroinium relatively high in carbon by electrically smelting a charge containing an excess of carbon, separating the resulting slag, heating a granular body of a decarburizing agent by interposing the body as a resistanceconductor in an electric circuit, percolating the molten high-carbon product through the heated granular body, and separating the carburized reagent from the low-carbon product, as set forth.

10. The process of producing lowcarbon ferrochromium, which consists in first producing ferrochromium relatively high in carbon, percolating the molten high-carbon product through a granular body of highly-heated lime, and separating the resulting calcium carbid from the low-carbon product, as set forth.

1]. The process of producing low-carbon ferrochromium, which consists in first producing ferrochromium relatively high in carbon,

heating a granular body of lime to a high temperature by interposing the body as a resistance-conductor in an electric circuit, percolating the molten high carbon product through the heated granular body, and separating the resulting calcium carbid from the low-carbon product, as set forth.

12. The process of producing low-carbon ferrochromium, which consists in first producing ferrochromium relatively high in carbon by electrically smelting a charge containing an excess of carbon, separating the resulting slag, heating a granular body of lime to a high temperature by interposing the body as a resistance-conductor in an electric circuit, percolating the molten high-carbon product through the heated granular body, and separating the resulting calcium carbid from the low-carbon product, as set forth.

In testimony whereof I atfiX my signature in presence of two witnesses.

EDGAR F. PRICE.

Witnesses:

C. E. BILLINGS, C. C. MosHER. 

